DESCRIPTION(provided by applicant): Calcium oxalate stone disease is a prevalent disease with limited preventative treatment options. Dietary oxalate makes an important contribution to urinary oxalate excretion and a strong body of evidence suggests it plays an important role in calcium oxalate stone formation. The long-term objective of this project is to develop a commercial product based on the oxalate-degrading bacterium, Oxalobacter formigenes, which can reduce the absorption of dietary oxalate when taken with meals. The first two specific aims are designed to test the safety and efficacy of this approach. In these studies normal, healthy volunteers will consume diets with controlled contents of oxalate and other key nutrients. In the first specific aim in an oxalate load study, which simulates a single meal, the optimal dose of bacteria required to reduce oxalate absorption from the load will be determined. In the second specific aim this dose will be used to determine the effects of bacteria taken with each meal for 4 days. The urinary excretion relative to that of creatinine will be used as an index of oxalate absorption in each study. The third specific aim will optimize fermentation and freeze drying conditions to produce a product with satisfactory cost, efficacy, safety and shelf life. Due to the wide spread occurrence of stone disease this product has the potential to be a viable treatment to prevent the formation of kidney stones. PROPOSED COMMERCIAL APPLICATION: Urolithiasis is a common disease with few therapies that are effective in eliminating recurrences in susceptible individuals. Thus there is a large market for a product that can reduce urinary oxalate excretion that could benefit all calcium oxalate stone formers. The proposed therapy is to degrade dietary oxalate in the GI tract before it could gen absorbed.